How to control and prevent pesky parasites: basics on worms, coccidia and other internal parasites

Dr. Christine PetersenDVM, PhDDepartment of Veterinary Pathology- Global Parasitology section, Iowa State University(515) 294-9013, kalicat@iastate.eduMay 2008

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Zoonosis

Pl. ZoonosesA disease such as rabies that can be transmitted from animals to peopleZoo- from Gk zoio- living being, animalindicates animals or animal formsNosos- illness (Gk)Adj- zoonotic

Overview- what will cover

HookwormsRoundwormsCoccidia (Isospora particularly-dogs/cats)GiardiaTritrichomonas

Parasitic diseases that are zoonotic

Do you see hookworms at your shelter/clinic?

Yes

No

How often do you diagnose hookworms?

All the time (daily to weekly)Sometimes (weekly to monthly)Only in the summertimeOccasionally (monthly)Rarely (a couple times a year)Never

Hookworms- scientific nameAncylostomatoidea

Anterior end is bent (hooked) Have highly cuticularized buccal capsule

Used to pierce GI wall and obtain blood

Adults occur in small intestine of dog/cat

Attach to host intestinal GI wall & suck blood

Buccal cavity of Uncinaria

showing cutting plates

Hookworms of dogs and cats

Ancylostoma caninumcommon hookworm of dogsvery rare in catsmost pathogenic hookworm in dogs/cats

A. tubaeformecommon hookworm of felids rare in dogs

Hookworms of dogs and cats

A. braziliensein both dogs and cats in tropics & subtropics

Uncinaria stenocephalanorthern hookworm found mainly in dogs not common in cats

Eggs of Ancylostoma (top) & Uncinaria (bottom)

•thin shell, oval to oblong, pale• non-embryonated in fresh feces (2-8 cell stage)Diagnosis:

Signalment, age and clinical signsthis is the only basis for ante-mortem diagnosis in per-acute neonatal ancylostomiasis

Detection of eggs in feces and/or worms at necropsy

Fecal flotation to detect eggsWorms grossly visible

Ancylostoma caninum

Very common in dogs of all ages in midwest

More significant problem in south & central US

Infectious larval stage (L3) survive best in moist, sandy-loam soils at moderate temperatures

do not survive freezing do not survive at temps >37 ºC

Clinical cases more common during warm weather

Uncinaria stenocephala

More prevalent in northern US

less common & less pathogenic than A. caninum because it sucks less blood

Structureeggs slightly larger than A. caninum

Lactogenic transmissionimportantNo prenatal transmission

Hookworm transmission

L3 (infective larvae) can be acquired by:1. Skin penetration 2. Ingestion

In food or waterLactogenic transmission: major source of infection of puppiesIngestion of arrested larvae in paratenic hosts

3. Transplacental route ~unimportant

Tracheal vs. somatic migration

Tracheal- Penetrate capillary and alveolar walls

Enter lumen of alveoli and migrate up airway to tracheaGet coughed up and swallowed Develop to adults in small intestine

Somatic- Remain in alveolar capillaries Blood flow carries L3 to musclesExit muscle capillaries and become hypobioticor arrested larvae

L3 acquired by ingestion

Undergo mucosal migrationEnter gastric glands or SI mucosa Most emerge in a few days & develop to adults

pre-patent period = 2-3 weeks

Some enter bloodstream from SI mucosa and undergo either tracheal or somatic migration

in older or infected dogs, most undergo a somatic migration to become arrested larvae in muscles

Fate of hypobiotic larvaein pregnant dog

Larvae are “activated”L3 occur in milk up to 20 days post-whelpingThese larvae develop directly to adults in puppy small intestine

blood-lung migration already completed in dam

Undergo lactogenic transmission to nursing pups

Possible transplacental transmission to fetal lung

Persistent hookworm infection

Source of infection: hypobiotic larvae in SI mucosa or muscles 1. Larvae “leak” out of these sites

~continuously and reach the SI lumenif animal already has adults in SI: probably shed into lumen and expelled if no hookworms present: develop to adults

2. If adult hookworms killed by an anthelmintic, arrested larvae can be activated and quickly repopulate the SI

Pathogenesis

Blood sucking & plug-feeding activities

attach to mucosa and pull a plug of intestinal mucosa into the buccal capsule use teeth to lacerate mucosasecrete proteolytic enzymes & anticoagulantchange sites frequently so old sites continue to bleed Leads to blood loss- anemia

Clinical signsVary from asymptomatic to rapidly fatal-not enough red blood cells (anemia)Severity depends upon:

dosage of infecting L3 age resistance and acquired immunity iron reserves (low in puppies) nutritional status

Clinical signs

↓ stamina with weaknesspale mucous membranesmelena or possible bloody feces unthrifty appearance (thin, rough hair coat)

Hookworm infection in neonatal pups

Results from massive milk-based transmissionSigns develop as early as 4 days of

ageworms start to suck blood after molting from L4 to L5 (immature adult stage)Can be fatal by 10-24 days of age even with treatment

Pups: extremely pale with bloody feces, diarrheaNO eggs in feces (yet):

Adults begin egg-laying at 16 DPIClinical signs usually occur ~7-14-days of age

Necropsy findings: blood & immature worms in intestinal tract

Hookworm infection in neonatal pups

Hookworm in older pups

Results from acquisition of large numbers of infectious larvae over short period of time

usually seen in older pupsgeneral pallor due to severe anemiaBlack feces- digested bloodoften die unless treated promptlyeggs in fecesadults worms and blood in SI

Hookworm in older dogsCompensated form:

dogs asymptomatic unless stressedfeces normal and contain low to moderate numbers of eggscommon in adult dogs with low number of worms

De-compensated form: in mature dogs, usually malnourishedmoderate number of worms + many eggsthin, rough hair coat, lethargicpale: anemiamelena: may develop bloody diarrhea can be fatal

Small intestine showing hemorrhagic lesions caused by hookworms

Treatment

Peracute neonatal ancylostomiasis AnthelminticSupportive care including blood transfusionPoor prognosis

Acute and chronic compensated form

AnthelminticChronic decompensated form

Anthelmintic plus nutritional support

Treatment

Anthelmintics effective against adult worms

butamisol dichlorvosdisophenol febantelfenbendazole* mebendazolemilbemycin* pyrantel pamoate

(Strongid)ivermectin* - effective dose is extra-label!*also effective against larvae

Prevention and control

Identify and treat infected dogs Sanitation: remove feces daily + cleaningGood flooring with no cracks

Coated concrete avoid gravel, sand, dirt, grass, damp shady areas Spray with 1% bleach (3c/gal)

Apply sodium borate (10 lbs/100 ft2) and rake inL3 killed by hard frost

Prevention and control

Worm bitches before breeding, during 3rd trimester of pregnancy and 2 weeks after whelping

Objective: kill migrating larvae and activated hypobiotic larvaeFenbendazole

Treat pups at 2, 4, 6, and 8 weeks of age

In area with high parasite burden weekly Tx for 3 monthsPyrantel suggested

Anthelmintics for prevention

Heartworm/hookworm preventatives:

ivermectin + pyrantelmilbemycinstyrid/caracideoxibendazole + diethylcarbamazine

Hookworms: Public health importance

Cause cutaneous larval migrans (CLM) linear, tortuous, erythematous and intensely pruritic eruptions caused by migration of nematode larvae in humans

Most commonly caused by A. brazilienseA. caninum, U. stenocephala, Bunostomum spp & Strongyloides spp. can also cause CLMKnown as “barnyard itch”, “creeping eruption”or “ground itch”

Cutaneous Larval Migrans

Hookworms (Ancylostoma and Uncinaria) can produce cutaneous larval migrans

Eggs are passedLarva develop and penetrate human skin- cases of walking barefoot in yard- AustraliaIngestion of worms leads to intestinal problems

Cutaneous larval migrans

Migration tunnels of larvae appear as ridges on skin surface

larvae want into bloodstream!!!cause intense iching that can persist for weeks to monthssecondary bacterial infection commonMore severe and persistent in persons hypersensitized by prior exposure

Rare cases of intestinal infection of humans with adult A. caninum

Hookworms

Prevention in humans involvesTreatment of infected animalsRoutine de-worming (CDC) Daily fenbendazole treatment of pregnant dogs from 40th day of gestation through 14th day of lactation shown to inhibit T. canis larvae in tissues- prevents or greatly reduces incidence of infection in puppiesCleaning the environment (pick up yard!!)Keeping pets from defecating in child play areas

Treatment in humansHandouts available from CDC for lobby area use, fast facts from CFSPH website

www.cfsph.iastate.edu

Questions?

Roundworms

Dogs, catsToxocara sp., Toxascaris

HorsesParascaris equorum

SwineAscaris suum

CattleNeoascaris (Toxocara) vitulorum

Ascarids of dogs and cats

Toxocara canis, T. catiToxascaris leoninaVery common & important roundworms

virtually all puppies & kittens are infected early in lifezoonotic: cause visceral & ocular larval migrans in humans

Toxocara canisCommon dog roundwormHosts

wild & domestic canids rarely in felids

Many animals can be paratenic hosts

rodents, rabbits, cattle, sheep, goats, birds, earthworms, etc

Do you see roundworms at your shelter/clinic?

Yes

No

Toxocara eggs

Round or ellipticalShell thick, rough Shell contents

Single cellVery darkAlmost fills shell

Eggs of Toxocara cati are similarto T. canis eggs, but smaller

Toxocara cati

Common roundworm of wild and domestic felids

Very common in kittens Rare in dogs

Common in feral cats, wild felids as result of ingesting paratenic hosts

rodents, chickens, birds, earthworms, cockroaches, ruminants etc.Milk based transmission onlyNO transplacental transmission!

Toxascaris leonina

Occurs in both dogs and cats of all ages

More common in dogs than cats in the Midwest

Not as prevalent as ToxocaraMixed infections with Toxocara occur

Toxascaris

Eggs of Toxocara andToxascaris

Life cycle of T. canisAdults in small intestine → eggs (lots!) in fecesInfective larva develops within eggin ~2-4 weeksEgg with larva ingestedLarva hatches in duodenumLarval migration:

pathway & fate of larvae varies with host age and susceptibilityyoung hosts<12 weeks: liver-lung-tracheal migrationolder hosts > 12 weeks: liver-lung-somatic migration

T. canis in pregnant dogs

Worm can cross placenta before pups born

Activation of hypobiotic larvae in last trimester Enter uterine circulation, cross placenta → fetal liver + lungsLarvae complete migration after birth

liver→ lung → trachea → GI track

T. canis in pregnant dogs

milk transmission to pupsHypobiotic larvae activated in late gestation & early lactation Migrate to mammary glandsPups ingest larvae in colostrum & milkIngested larvae mature in GI track

Life cycle of T. canisMales, non-pregnant or spayed females

Granulomas = dead end for hypobiotic larvae

Small rodents, prey species (paratenic hosts)

larvae from ingested egg undergo somatic migration hypobiotic in tissuessurvive in granulomas for several yearsdevelop directly to adults in ~3 weeks if dog ingests paratenic host

Epidemiology

Transplacental transmission is most common route of infection

Very common in puppies & young dogs

Patent infections more common in males than femalesSmall rodents reservoir of infection

may be common source of infection for rural and feral dogs

Epidemiology

Adult worms survive ~4 monthsPups expel most worms by 6 mos of age

irritation of intestine or “self-cure”??

Eggs infective in >2 weeks in environment

Very hardy - resist environmental extremes

Persist in soil for yearsKilled by direct sunlight and heat

Summary: T. canis transmission

Transplacental transmission to fetal liver via activated hypobiotic larvae in bitchIngestion of:

Egg in environment with infective larvaLarvae from colostrum or milk of dam Hypobiotic larvae in paratenic host tissuesEggs, larvae or immature worms in puppy vomit or feces

Clinical signs: T. canis

Due to transplacental transmission

In utero (fetal pups)migrating larvae can damage liver cause fetal death or stillbirths

Newborn puppiesWeak pups due to liver & lungdamage by migrating larvae Lung hemorrhages, pneumoniaMay die at 2-3 days of age

Typical clinical signs in pupsPot-bellyIll thrift Dull dry hair coatAbdominal discomfortVomitingMucoid diarrhea

may alternate with constipation

Toxocara in vomit/feces

Clinical signs in pupsworst case scenarios

Aspiration pneumonia (vomiting)Obstruction of bile or pancreatic ductsObstruction of SI with possible ruptureCNS signs can occur in heavy infections

Cause?Recover with anthelmintic treatment

Death ~2-3 wks of age

Clinical signs older dogs

Adults usually asymptomaticfew adult ascarids present in SIingestion of large number of eggs can result in vomiting with bloody enteritis

Encapsulated larvae in tissues rarely cause clinical signs

possible CNS problems (convulsions) associated with larval death in brain

Clinical signs of T. cati infection

Type & severity of signs determined by:

host ageinfecting parasite stage infecting dose of parasitelocation of infecting stage

Not as pathogenic as T. canisAdult cats usually asymptomatic

Toxocaracati in the small intestineof a cat.

How often do you diagnose roundworms?

All the time (daily to weekly)Sometimes (weekly to monthly)Only in the summertimeOccasionally (monthly)Rarely (a couple times a year)Never

Diagnosis of Toxocara infection

History plus clinical signsprevious infection in litter, kennel etc.

Presence of Toxocara in feces and/or vomitusDetection of typical eggs in feces

Fecal flotation

Treatment of Toxocara infection

For dogs: Anthelmintics for treatment of intestinal stages:

ivermectin @ 0.1-0.2 mg/kg orally NOT for collies, collie like breeds (shelties, border collies, etc.)!Extra-label at dosages >0.006 mg/kg

ivermectin plus pyrantel (Heartguard Plus)milbemycin piperazinepyrantel pamoate dichlorvos

fenbendazole

Treatment of T. canis infection

Anthelmintics with activity against larvae

fenbendazole for pregnant bitchkills only larvae activated during pregnancyneed ~continuous treatment

Prevention of T. canis

Decrease environmental contamination with eggs

deworm all infected dogsdeworm puppies before infection becomes patent

recommend treatment at 2, 4, 6 and 8 wks of age

strict hygiene practices

Treatment: cats

Similar to treatment of Toxocara in dogs

Fewer anthelmintics approved for catsFenbendazole (10 mg/kg for 3 days orally)Febantel approved for cats and effective

Treat kittens at 3, 5, 7 and 9 wks of ageEvaluate cats of all ages for eggs in feces and treat as needed

Prevention of Toxocara

Reduce numbers of somatic larvae in breeding females

reduce exposure to infective eggs by sanitationdeworm at time of breeding and during lactation (2-3 weeks post-whelping)

Prevent ingestion of rodents

Baylisascaris procyonisRaccoon roundworm

Very common in raccoons in North AmericaAdults and egg similar to ToxocaraIngestion egg with infective larva Undergo liver-lung-tracheal migrationNonpathogenic in raccoons, can also infect dogs

Paratenic hosts have arrested larvae in tissues

Baylisascaris fromthe small intestine of a raccoon

Eggs of hookworm, Toxocara, and Baylisascaris (B)

T

B

Do you see raccoon roundworms at your shelter/clinic?

Yes

No

Public health significance

Ingestion of egg with larvaeLarvae highly invasive & pathogenic Often in CNS of non-raccoon hosts including man

Infection in abnormal hostspossible respiratory signsNervous system signs: can mimic rabies

Prevention and controlTreat captive raccoons with anthelmintic

Wormers effective against dog and cat ascarids should be effective against B. procyonis

Keep wild raccoons out of barns, sheds Pick up & destroy raccoon fecesWash hands after handling raccoons

Visceral larval migrans (VLM)

a single female roundworm can produce more than 100,000 eggs/dayOnce eggs become infective can remain infective in the soil for yearsMost commonly caused by T. canis in humansCan also be caused by: Baylisascaris procyonisLess frequently caused by Toxocara cati, Toxascaris leonina, Ascaris suum

Pathogenesis

Sandboxes, playgrounds etc. frequently contaminated with dog/cat feces

children ingest dirt/sand with infective ascarid eggslarvae hatch in intestine & attempt normal migration pathwayinvade lungs, liver, eyes, brain etc. and cause disease

Human VLM

Most common in children <6 yrs oldClinical signs and lab findings include:

Irritability, intermittent fever, loss of appetite, weight lossAching muscles, nausea, swelling, itching Enlarged liver, inflamed lungs Immune responses to parasites (eosinophils, IgE)

Diagnosis

History of picaClinical signsDetection of larvae by biopsy (liver or lung)Serology

ELISA

Ocular larval migrans

Sequel to VLMLarvae of T. canisinvade human eyeCause unilateral inner eye lesion similar to retinoblastomaTreatable

Ocular larval migrans

Granuloma caused by larval Toxocara canis in eye

Questions?

Coccidia- Isospora spp.

Disease: isosporosis; coccidiosisVery common parasitesLife cycle fecal-oral transmission of sporulated oocyst

Addition of rodents in dog and cat spp.

Rodent paratenic hosts

dog and cat Isospora spp. Rodent ingests sporulated oocysts

sporozoites released in GI tractpenetrate gut wall, enter extra-intestinal cellseach sporozoite forms a monozoic cystsporozoite remains viable but does not develop

definitive host ingests rodentsporozoite released from monozoic cystinitiates merogony in cat/dog intestine

Isosporosis of cats and dogs

Each host parasitized by >1 Isospora spp.Location of life cycle stagesLocation of life cycle stages

Unsporulated oocysts shed in fecesUnsporulated oocysts shed in fecesSporogony in environmentSporogony in environmentMerogony & gametogony in small Merogony & gametogony in small intestineintestine

Isosporosis in cats and dogs

Usually non- or mildly pathogenicCan cause severe enteritis (pups & kittens)

Signsanorexia, weight lossmucoid to bloody diarrhea possible vomitingdehydration possible anemiacan be fatal

Significant problem in kennels and catteries

Diagnosis: isosporosis in cats and dogs

Age, history and clinical signs A differential in cases of diarrhea, esp. puppies and kittensdetect oocysts in feces

non-sporulated in fresh feces

clinical signs precede oocyst shedding

Sporulated oocyst ofIsospora rivolta

Treatment of isoporosis

Sulfonamides Sulfadimethoxine (Albon)Trimethoprim-sulfadiazine (Tribrissen)Amprolium (Corid) – extra-label

Supportive care

Control of isosporosis

Sanitationsteam cleaning, boiling water, ammonium hydroxide, bleach

Post-partum treatment of cat or dogProphylactic treatment of offspring

extra-label use of coccidiostatamprolium (thiamine antagonist) or decoquinate

Questions?

Giardia lamblia

Trophozoites

Giardia lamblia

Synonyms: G. duodenalis, G. intestinalisInfects wide range of mammalian hosts Comprised of several “Assemblages”

Some assemblages zoonoticHuman to human transmission probably more common

Giardia lamblia genotypes

Assemblage A : zoonoticHumans, livestock, dog, cat, beaver, guinea pig, deer, prairie dog, bobcat, others

Assemblage B: zoonoticHumans, cattle, dog, cat, beaver, muskrats, rat, others

Assemblages C & D: primarily infect dogsAssemblage E: artiodactyl speciesAssemblage F: cats

Prevalence of Giardia

Most common human intestinal parasite~7% of humans

~10% of household dogs and catsGreatest prevalence in young and in kennels or catteries Japan survey of dog breeding kennels (2005)

100% of kennels positive for Giardia54.5% of pups vs. 30.9% of adults

7.3% of cats <1 year old in NY in 20017.2% of 1216 dogs seen in vet clinics in Canada

Prevalence of Giardia

Increasing reports from calves, lambs, kids, foals

Ruminants from 2 weeks - 2 months oldRecent US study in calves

began shedding cysts at 4 days of age peak numbers at 14 days of age

Foals 2 weeks to ~6 months old

Life cycle: directCysts ingested with food or water contaminated by feces

Cysts survive weeks to months in cool, moist conditionsContaminated water important source of infection

Cysts excyst in small intestine

Duodenum (dogs) or jejunum/ileum (cats)

Giardiatrophozoite showing flagellaand two nuclei

Trophozoite of GiardiaWhat characteristicof the diplomonadsis evident?

Pathogenesis

Trophozoites attach/detach from gut epithelial cellsInfection results in:

Villous atrophy Diffuse loss of microvillous brush borderDisaccharidase insufficiencyImpaired absorption

Electrolytes, nutrient, waterResults in diarrhea

Giardiasis

Spectrum varies from asymptomatic carriage to severe diarrhea and malabsorption.

Acute giardiasis-develops after 5-6 day incubation period -usually lasts 1 to 3 weeks-diarrhea, abdominal pain, bloating, nausea, and

vomiting.

Chronic giardiasis -acute symptoms are recurrent -and malabsorption and debilitation may occur.

Clinical features-humans

Clinical signs-animals

Persistent diarrheaCharacter of feces

Liquid to semi-formedPale & malodorous↑ mucus (especially in cats)Steatorrhea

↑ Borborygmi

Clinical signs-animals cont

AfebrileBright & alertNot anorexic Rarely see melena, vomiting, serious dehydrationChronic giardiasis can result in weight loss, retarded growth

Diagnosis

Clinical signs are relatively non-specific

Numerous differentials

Always do a fecal exam on an animal with diarrhea to obtain a definitive diagnosis of giardiasis

Definitive diagnosis-fecal flotation

Trophozoites more likely in loose stoolsNeed fresh feces kept cool and examined asap or preserved promptly

Wet mount of fresh sample -”falling leaf”Stained smear (Dif-Quik works well)Can also find trophozoites in small intestinal samples collected by endoscopy or laparotomy

Definitive diagnosis-fecal flotationCysts more likely in semi-formed or formed feces Best method: centrifugal flotation in zinc sulfate

sugar distorts cystsCysts shed intermittently

1 exam detects ~77% of positive dogs3 exams detect ~95% of positive dogs

Recommend fecal exams every other day X3

Definitive diagnosis-other methods

IFA - detects cysts using fluorescent antibodyELISA – detects antigen in feces

SNAP Giardia, IDEXXProSpecT Giardia Rapid Assay, Alexon

Check with lab for sample submission Submit fresh chilled or formalin-fixed fecesDilute feces in 5-10% NBF and/or PVA

Definitive diagnosisComparative studies: IFA and ELISA tests comparableBoth are more sensitive and specific than zinc sulfate flotation method

NOTE: cysts disappear temporarily after barium enema, laxatives, kaopectate...

Treatment – all extra-labelMetronidazole - human drugFenbendazole:

Labeled for helminth infections - dogs, cats, cattle, horses & pigsSafest for pregnant dog

Febantel – metabolized to fenbendazoleAlbendazole

Effective but not recommended because of serious potential side-effects

Treatment & control

Refractory casesIs re-infection occurring? Repeat treatment with same, different or a combination of drugs

Sanitation important Vaccine available

GiardiaVax – Ft. DodgeAdditional tool for use in treatment and control

Questions?

Tritrichomonas foetus

Worldwide venereal disease of cattle

Bovine trichomoniasis

Higher prevalence in older bulls (vs. young)

bulls >4 yrs old = permanent carriersfunction of preputial epithelium structure

More common in beef herds than dairyFinding in shelter cats in IA, CO- why?

Transmission- cows

Trophozoite stage only (No cyst)Mechanical transmission during coitusIatrogenic

AI: bull semen to cow or cow to cow (repro exam)

Bull to bull transmission possible

Use of same artificial vagina by infected and clean bull within short time frame

Photo courtesy of Dr. Diane Addie

Diagnostic characteristics of Tritrichomonas foetus

Feline trichomoniasis

Large bowel diarrhea caused by a trichomonad indistinguishable from T. foetus

Morphology: light, transmission, and scanning electron microscopy rRNA gene sequence analysisRFLP-PCR

Feline trichomoniasis

Cases reported from 12 states Alaska to FloridaAlso reported in England, Scotland, Germany

More prevalent in shelters, cat colonies and multi-cat householdsMost commonly affects cats <1 yr oldCat to cat spread believed to occur via direct contact

Questions?

Resources on this topic:

Georgis’ parasitology for veterinarians, 8th ed, 2003CFSPH Technical Fact Sheets- for instance, Baylisascariasis, at http://www.cfsph.iastate.edu/DiseaseInfo/default.htmCDC web site. Baylisascariasis at http://www.cdc.gov/ncidod/dpd/parasites/baylisascaris/default.htmCAPC web site (although sponsored by Pharmacompanies, so very pro-year round preventatives), for example, ascarids at http://www.capcvet.org/?p=Guidelines_Ascarid&h=0&s=0